The Mandarin spoken in Shanghai differs in some aspects from the Mandarin spoken in Beijing. One of the most notable differences is a merging of the retroflex consonants with the non-retroflex ones (Zheng, Sproat, Gu, Shafran, Zhou, Su, Jurafsky, Starr, & Yoon, 2005). Based on quantitative analysis of three pairs of phonological variables [ʂ] vs. [s], [tʂh] vs. [tsh], and [tʂ] vs. [ts], this thesis takes up the study of retroflex and non-retroflex merger in Shanghai-accented Mandarin, by using recorded interviews to explore whether such variation is correlated with social class, age, gender and task formality. The statistical results indicate that social class, age and task formality all have a significant effect on retroflex and non-retroflex merger for Shanghainese. Gender, however, was shown not having a strong correlation with retroflex and non-retroflex merger.